RICHMOND, Virginia (CNN) --Democratic presidential front-runner John Kerry said Saturday he would challenge the Bush administration as "extreme" and out of touch with mainstream America if he goes up against President Bush in November.

"I don't think they're mainstream at all," he said. "And I think Americans want change and want to move in a stronger position for our country."

Kerry picked up a sweep in Saturday's caucuses with projected wins in Michigan and Washington state.

The Massachusetts senator delivered a speech Saturday night that began with a nod to his victory.

"I want to give a very special thank you to the state of Washington and the state of Michigan for giving us great victories today. We are deeply appreciative for that," Kerry said.

"A great message is being sent across the country from Michigan and Washington state, the same message that was sent in Iowa and New Hampshire and Missouri and other states across this country. And that is the same message that I'm carrying to Virginia and to Tennessee and to the rest of this country and that message is, 'George Bush's days are numbered and change is on the way.'"

Kerry's speech centered on tough criticism of Bush and his administration.

He said the current administration has abandoned "mainstream values" to pursue policies "fundamentally at odds with our history."

Kerry told supporters, who cheered loudly, that America is going in the wrong direction and, if elected, he would "turn it around from the radical course that George Bush and his extreme friends are taking us."

The Massachusetts senator said President Bush has weakened the country both at home and abroad, by running up record budget deficits and overextending the military.

Kerry, known to be an aggressive campaigner, said he was prepared for attacks by what he called "the Republican smear machine," saying, "I am one Democrat who knows how to fight back and I've only just begun to fight."

Republican National Committee Chairman Ed Gillespie has attacked Kerry's Senate record on national security issues, while carefully acknowledging his service as a decorated Navy officer in Vietnam.

"This week George Bush and the Republican smear machine have begun to trot out the same old lines of attack, Kerry said. "They've used those lines of attack to try to blur the real issues before this country. They've used this to divide us before and I have news this time for George Bush and Karl Rove and Ed Gillespie and the rest of their friends, I am not going to back down."

Prior to the event, and his victories, Kerry spent the day painting Bush as an extremist.

"In the face of the Bush administration's failures, we know what kind of campaign the Bush attack machine will run," Kerry said. "They did it to my friend John McCain in South Carolina in 2000. They did it to my friend Max Cleland in Georgia in 2002. Well, it's not going to work in 2004, for a very simple reason: They're extreme. We're mainstream, and we're going to stand up and fight back."

Earlier this week, Kerry picked up the endorsement of the American Federation of Teachers union, with its 1.3 million members. The AFT is the fifth-largest union in the AFL-CIO and the only major union headed by a woman. Its membership is 70 percent female.

He was endorsed Friday by former rival Rep. Dick Gephardt of Missouri, who had been a favorite of organized labor before dropping out of the race last month.

Kerry has finished first in nine of the 11 states that have held primaries or caucuses. His victories started with an unexpected win in Iowa, which boosted him to front-runner status.

In the months before the Iowa and New Hampshire contests, Kerry's campaign had become mired in conflict, leading to the dismissal of his campaign manager in November.

Kerry continued to trail Dean in polls until just a couple of weeks before Iowa's January 19 caucus.

After months of being pounded by Dean for supporting a resolution authorizing President Bush to use military force in Iraq, Kerry turned the tables in the closing weeks of the campaign, pointing out his national security experience as a senator and a Vietnam war veteran.

Kerry has kept the same message with proven success as he turned his campaign to the national stage.